Methods of forming packaged semiconductor light emitting devices having front contacts by compression molding

ABSTRACT

Methods of packaging a semiconductor light emitting device include providing a substrate having the semiconductor light emitting device on a front face thereof and a contact on a front face thereof, wherein the light emitting device is electrically connected to the contact on the front face of the substrate. The substrate is compression molded to form an optical element on the front face of the substrate over the semiconductor light emitting device and a residual coating over a region of the front face of the substrate including the contact. The residual coating over the contact may be removed without damaging the contact. Packaged semiconductor light emitting devices are also provided.

BACKGROUND OF THE INVENTION

This invention relates to semiconductor light emitting devices andmanufacturing methods therefor, and more particularly to packaging andpackaging methods for semiconductor light emitting devices.

Semiconductor light emitting devices, such as Light Emitting Diodes(LEDs) or laser diodes, are widely used for many applications. As iswell known to those having skill in the art, a semiconductor lightemitting device includes one or more semiconductor layers that areconfigured to emit coherent and/or incoherent light upon energizationthereof. It is also known that the semiconductor light emitting devicegenerally is packaged to provide external electrical connections, heatsinking, lenses or waveguides, environmental protection and/or otherfunctions.

For example, it is known to provide a two-piece package for asemiconductor light emitting device, wherein the semiconductor lightemitting device is mounted on a substrate that comprises alumina,aluminum nitride and/or other materials, which include electrical tracesthereon, to provide external connections for the semiconductor lightemitting device. A second substrate, which may comprise silver platedcopper, is mounted on the first substrate, for example, using glue,surrounding the semiconductor light emitting device. A lens may beplaced on the second substrate over the semiconductor light emittingdevice. Light emitting diodes with two-piece packages as described aboveare described in Application Serial No. US 2004/0041222 A1 to Loh,entitled Power Surface Mount Light Emitting Die Package, published Mar.4, 2004, assigned to the assignee of the present invention, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein.

With multipart mounting packages for semiconductor light emittingdevices, the different parts are typically made of different materials.As a result, the thermal impedance for such packages may be higher and athermal mismatch may result among the various components within apackage that may cause reliability problems with a package. For example,problems may result at an interface between a copper metal of a heatsink or cavity with a plastic of a body in which such a heat sink orcavity is mounted. In addition, assembly may be more complicated becauseof increased piece part counts for the package. In addition, where asheet metal optical cavity is utilized, a cavity typically can only befabricated in a limited range of depth and shape configurations. Suchmultipart packages may also have a larger optical cavity space,resulting in greater volumes of encapsulant being used, which mayincrease problems related to delamination and/or formation of bubbleswithin the encapsulant during temperature cycles.

The use of a pre-molded lens attached by adhesive may encounter someproblems in robustness and reliability of the finished product. Forexample, the manufacturing process for such devices may be inherentlyinconsistent and the resultant package may be less robust and/orreliable. It is also known to form the lens using a dispensing methodcapitalizing on the viscosity of a resin used in forming the lens.

In some applications, it may be preferred to mount the LED on a surfaceof a substrate, such as a ceramic substrate, a metal core printedcircuit board (MCPCB), a flexible circuit substrate and/or a lead frame,without use of a reflector cup. However, where no such structure isprovided, it may be more difficult to form and/or secure a lens asvarious of the approaches described above may not be well suited to usewhere the LED is not positioned within a cavity.

It is also known to use transfer molding of epoxy to encapsulate certainlow power LED packages, such as miniature surface mountable devicesavailable from from Hewlett Packard Corporation. The epoxy on suchdevices may provide the structural strength to the package as well asencapsulating the devices inside. However, epoxy tends to be degraded bythe electromagnetic energy of blue light, generally generated by somesemiconductor light emitting devices, and may become less transmissiveto light as a result. The resulting package may, therefore, becomedimmer over a relatively short period of time. As such, epoxy may be aless attractive option for encapsulating devices that emit blue light.In addition, epoxy generally has a Coefficient of Thermal Expansion(CTE) mismatch problem with silicone soft gel, which may be used tojunction coat the LED chips and their bond wires as the first layer ofencapsulant.

It is also known to use casting to encapsulate LED devices with epoxy.This process typically can only be applied to an open chamber, wherecuring may occur with the epoxy contained in a cup and a lead frame maybe inserted inside the cup and be casted when the epoxy is cured. Duringcuring, a level of liquid epoxy is generally free to adjust itself as aresult of chemical reactions and shrinkage in volume.

Another approach uses compression molded lenses formed of silicone.Using compression molding, an array of compression molded lenses may beplaced over a matching array of LED chips on a substrate or wafer.However, conventional compression molding of lenses generally requiresthe use of electrical contacts on the back side, rather than the frontside, of the substrate as the molding material may extend across andlimit formation of electrical connections with front side contacts.

Packaging of semiconductor light emitting devices may add cost to theresulting packaged device due to the precision required for variousoperations. The costs typically increase as packaged light emittingdevices having different optical properties are required. Whilecompression molding technology has been proposed that could lower thecost for forming packaged light emitting devices, benefits of thistechnology have not been fully realized. For example, such techniqueshave generally only been used to produce simple lenses made of onematerial.

SUMMARY OF THE INVENTION

Some embodiments of the present invention provide methods of packaging asemiconductor light emitting device, including providing a substratehaving the semiconductor light emitting device on a front face thereofand a contact on a front face thereof, wherein the light emitting deviceis electrically connected to the contact on the front face of thesubstrate. An optical element is compression molded on the front face ofthe substrate over the semiconductor light emitting device and aresidual coating may be concurrently compression molded over a region ofthe front face of the substrate including the contact. The residualcoating over the contact may be removed without damaging the contact.

In other embodiments, providing a substrate includes mounting thesemiconductor light emitting device on the front face of the substrateand attaching a wire bond electrically connecting the semiconductorlight emitting device to a contact portion of the substrate. A secondsemiconductor light emitting device may be mounted on a back face of thesubstrate and electrically connected to a contact on the back face ofthe substrate. Compression molding the optical element may includeforming the optical element over the semiconductor light emitting deviceand the wire bond and directly contacting the wire bond. The substratemay be a ceramic substrate, a metal core printed circuit board (MCPCB),a flexible circuit substrate and/or a lead frame.

In further embodiments, compression molding the optical element ispreceded by providing a mask covering the front side contact andremoving the residual coating includes removing the mask. The mask maybe a polyimide film. Removing the mask may include cutting the residualcoating in a pattern corresponding to the mask and removing the mask andthe overlaying residual coating thereon to expose the front sidecontact.

In other embodiments, the substrate includes a plurality ofsemiconductor light emitting devices and contacts on the front facethereof and compression molding the optical element includes forming aplurality of optical elements on the front face of the substrate overcorresponding ones of the semiconductor light emitting devices and aresidual coating over a region of the front face of the substrateincluding the plurality of contacts. For example, cutting the residualcoating may include cutting the residual coating with a hot knife and/orwire mesh. The hot knife and/or wire mesh may have a patterncorresponding to the pattern cut in the residual coating.

In further embodiments, the optical elements comprise lenses andcompression molding includes placing the substrate in a mold including aplurality of lens shape cavities positioned proximate corresponding onesof the plurality of semiconductor light emitting devices, providingsilicone into the mold, compression molding the lenses from the siliconein the cavities and removing the substrate with the lenses formedtherein from the mold. Providing silicone may be preceded by providing arelease layer on a surface of the mold including the cavities andremoving the substrate may include removing the substrate at the releaselayer.

In yet other embodiments, the substrate is a flexible circuit substrateand removing the residual coating includes wet solvent chemical cleaningthe substrate to remove the residual coating over the contact. Removingthe residual coating may be performed using a laser, mechanical sawand/or the like in some embodiments.

In further embodiments, the optical element is a first and a secondoptical element and compression molding the optical element includescompression molding the first optical element proximate thesemiconductor light emitting device and compression molding the secondoptical element over the semiconductor light emitting device and thefirst optical element. Compression molding the first optical element mayinclude compression molding the first optical element over thesemiconductor light emitting device.

In some embodiments compression molding the optical element is precededby forming a first optical element proximate the semiconductor lightemitting device and compression molding the optical element includescompression molding a second optical element over the semiconductorlight emitting device and the first optical element.

In yet further embodiments of the present invention, packagedsemiconductor light emitting devices include a substrate having acontact on a front face thereof. A semiconductor light emitting deviceis mounted on the front face of the substrate. A compression moldedoptical element is on the front face of the substrate over thesemiconductor light emitting device.

In further embodiments, the semiconductor light emitting device ismounted flush on the front face of the substrate without a reflectorcavity and the optical element is molded to and extends from the frontface of the substrate in a region surrounding the semiconductor lightemitting device and extends over the semiconductor light emittingdevice. The optical element may be a second optical element and thedevice may further include a first optical element positioned proximatethe semiconductor light emitting device and the second optical elementmay extend over the first optical element. The first optical element maybe a compression molded optical element. The compression molded opticalelement may be a silicone lens. The second optical element may be a lenshaving different optical properties than the first optical element. Forexample, the second optical element may have a phosphor or other lightscattering, luminescent and/or diffusing material therein.

In other embodiments, the semiconductor light emitting device is aplurality of semiconductor light emitting devices and the contact is aplurality of contacts on the front face. The compression molded opticalelement is a plurality of compression molded optical elements overcorresponding ones of the semiconductor light emitting devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a packaged semiconductor light emittingdevice according to some embodiments of the present invention.

FIG. 2 is a top plan view of a packaged semiconductor light emittingdevice according to further embodiments of the present invention.

FIGS. 3 through 6 are cross sectional views illustrating a method offorming the packaged semiconductor light emitting device of FIG. 2 takenalong line A-A of FIG. 2 according to some embodiments of the presentinvention.

FIG. 7 is a cross sectional view of a packaged semiconductor lightemitting device according to other embodiments of the present invention.

FIG. 8 is a cross sectional view of a packaged semiconductor lightemitting device according to further embodiments of the presentinvention.

FIG. 9 is a flow chart illustrating operations for forming a packagedsemiconductor light emitting device according to some embodiments of thepresent invention.

FIG. 10 is a flow chart illustrating operations for forming a packagedsemiconductor light emitting device according to other embodiments ofthe present invention.

DETAILED DESCRIPTION

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which embodiments of the invention are shown.This invention may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventionto those skilled in the art. In the drawings, the size and relativesizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Embodiments of the present invention are described herein with referenceto cross-section illustrations that are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, an etched region illustrated as a rectanglewill, typically, have rounded or curved features. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region of a device andare not intended to limit the scope of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andthis specification and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

Embodiments of packaged semiconductor light emitting devices and methodsfor forming the same will now be described with reference to FIGS. 1-9.Referring first to FIG. 1, a packaged semiconductor light emittingdevice 100 is schematically illustrated in top plan view. Moreparticularly the illustrated device 100 is shown as including asubstrate 105 having a plurality of semiconductor light emitting devices108 mounted in array arrangement on a front face 107 of the substrate105. A compression molded optical element 110, shown as a lens, isformed on the front face 107 of the substrate 105 over respectivesemiconductor light emitting devices 108.

The semiconductor light emitting device(s) 108 can comprise a lightemitting diode, laser diode and/or other device which may include one ormore semiconductor layers, which may comprise silicon, silicon carbide,gallium nitride and/or other semiconductor materials, a substrate whichmay comprise sapphire, silicon, silicon carbide, gallium nitride orother microelectronic substrates, and one or more contact layers whichmay comprise metal and/or other conductive layers. The design andfabrication of semiconductor light emitting devices are well known tothose having skill in the art.

For example, the light emitting device(s) 108 may be gallium nitridebased LEDs or lasers fabricated on a silicon carbide substrate such asthose devices manufactured and sold by Cree, Inc. of Durham, N.C. Forexample, the present invention may be suitable for use with LEDs and/orlasers as described in U.S. Pat. Nos. 6,201,262, 6,187,606, 6,120,600,5,912,477, 5,739,554, 5,631,190, 5,604,135, 5,523,589, 5,416,342,5,393,993, 5,338,944, 5,210,051, 5,027,168, 5,027,168,4,966,862 and/or4,918,497, the disclosures of which are incorporated herein by referenceas if set forth fully herein. Other suitable LEDs and/or lasers aredescribed in published U.S. Patent Publication No. US 2003/0006418 A1entitled Group III Nitride Based Light Emitting Diode Structures With aQuantum Well and Superlattice, Group III Nitride Based Quantum WellStructures and Group III Nitride Based Superlattice Structures,published Jan. 9, 2003, as well as published U.S. Patent Publication No.US 2002/0123164 A1 entitled Light Emitting Diodes IncludingModifications for Light Extraction and Manufacturing Methods Therefor.Furthermore, phosphor coated LEDs, such as those described in UnitedStates Patent Application No. US 2004/0056260 A1, published on Mar. 25,2004, entitled Phosphor-Coated Light Emitting Diodes Including TaperedSidewalls, and Fabrication Methods Therefor, the disclosure of which isincorporated by reference herein as if set forth fully, may also besuitable for use in embodiments of the present invention.

In still other embodiments, a drop of a material such as epoxy thatcontains phosphor therein may be placed on the semiconductor lightemitting device. LEDs that employ phosphor coatings are described, forexample, in U.S. Pat. Nos. 6,252,254; 6,069,440; 5,858,278; 5,813,753;5,277,840; and 5,959,316.

Also shown on the front face 107 of the substrate 105 is a plurality ofelectrical contacts 115. For example, the contacts 115 may be goldplated electrical contact pads connecting the semiconductor lightemitting devices 108 to electrical circuits, power sources and the like.It will be understood that, while only contacts on the front face 107are discussed herein, backside contacts may also be provided in someembodiments.

As will be described further herein, methods are provided in certainembodiments of the present invention whereby a compression molded lenses110 may be formed on front face 107 of the substrate 105 while stillusing front face contacts 115 and allowing electrical connections to thefront face 107 without interference from residual deposits of thenon-conductive material used to form the lenses 110. Furthermore,residual silicone used in forming the lenses 110 may remain on thesurfaces of the front face 107 to which no electrical contact isrequired in some embodiments of the present invention.

It will be understood that the arrangement shown in FIG. 1 is forexemplary purposes and that a variety of different configurations andcombinations of one or more semiconductor light emitting devices 108 andcontacts 115 may be included in the package semiconductor light emittingdevice 100 in various embodiments of the present invention, includingdevices having only a single light emitting device 108. Similarly, itwill be understood that the structure 100 illustrated in FIG. 1 may, insome embodiments, be further processed with portions thereof separatedto provide a plurality of discrete packaged semiconductor light emittingdevices formed from the illustrated device 100.

Depending on the embodiments, the substrate can included embeddedelectrical connections to form a string or cluster of LEDs betweenelectrical contacts 115 to provide individual front side contact LEDsand/or strings or clusters of LEDs. Additionally, the individual LEDswith lenses can each include contacts to enable the LEDs.

Semiconductor light emitting devices 108 may, in some embodiments of thepresent invention, be mounted flush on the front face 107 on thesubstrate 105 without a reflector cavity surrounding the light emittingdevices 108 as seen, for example, in FIG. 7.

A packaged semiconductor light emitting device 200 according to furtherembodiments will now be described with reference to the schematicillustration of FIG. 2. As shown in the embodiments FIG. 2, the packagedsemiconductor light emitting device 200 includes a substrate 205 and aplurality of light emitting devices 208 mounted flush on a front face207 of the substrate 205. A plurality of electrical contacts 215 areshown on the front face 207 proximate the semiconductor light emittingdevices 208. Also shown in FIG. 2 is a mask 230 covering the front sideof contacts 215. As illustrated in FIG. 2, the mask 230 may not entirelycover the totality of the surface area of the contacts 215.

The semiconductor light emitting devices 208 are illustratedschematically in FIG. 2 as having a circular shape. However, it will beunderstood that the shape of the semiconductor light emitting devices208 may vary and the circular representation is for purposes ofdescribing the present invention. Furthermore, the compression moldedlens 110 structures are not shown in FIG. 2. The particular arrangementof the front side contacts 215 relative to the light emitting devices208 and the number of front side contacts 215 is for illustrativepurposes and other arrangements may be provided in accordance with someembodiments of the present invention.

Methods of forming a packaged semiconductor light emitting deviceaccording to some embodiments of the present invention will now bedescribed with reference to the cross-sectional illustrations of FIGS.3-6 and the flow chart illustration of FIG. 9. The cross-sectionalillustrations of FIGS. 3-6 are taken along the line A-A of FIG. 2. Assuch, it will understood that, as with the description of FIG. 2, theparticular arrangement of contacts 215 and light emitting devices 208 inFIGS. 3-6 is for purposes of description of the present invention andthe methods of the present invention are not limited to the particularstructure or arrangement of components illustrated in the Figures.

As will be described with reference to the Figures, some embodiments ofthe present invention provide methods for forming packaged semiconductorlight emitting devices with molded compression lenses and front faceelectrical contacts on a substrate. The substrate may be, for example, aceramic substrate, a metal core printed circuit board (MCPCB), a flexcircuit and/or a lead frame. For the embodiments illustrated in FIGS.3-6, a mask or stencil, such as a polyimide film, is applied to thecontacts on the substrate prior to molding. After the compression moldedlenses, such as silicone lenses or the like, are applied to thesubstrate, a hot screen or other removal method can be used to removethe lens forming material from the front side contacts covered by themask or stencil. However, it will be understood that further embodimentsof the present invention provide manufacturing of packaged semiconductorlight emitting devices including compression-molded lenses without theuse of a mask or substrate. Also, different types of masks can be usedas well as different methods may be used for removing residual lensforming material, such as a laser, saw, hot knife, hot wire grid and/orwire mesh.

As seen in the embodiments illustrated in FIG. 3, an assembly 200including a substrate 205 with semiconductor light emitting devices 208and front side contacts 215 on a front face 207 thereof is provided. Asnoted above, in the illustrated embodiments, a mask 230 is also providedcovering the front side contacts 215. Also shown schematically in FIG. 3is a compression mold 305. Mold 305 is provided with indentations orcavities 320 shaped as lenses. A cavity 320 is provided for eachrespective one of the illustrated plurality of light emitting devices208. Silicone 315 is placed over the mold 305 and in the indentations320. As also shown in FIG. 3, a release layer 310 may also be usedbetween the silicone 315 and the mold 305. The release layer 310 mayfacilitate removing the mold 305 at the release layer 310 aftercompression molding of lenses from the silicone 315. The release layer310 may be, for example, Aflex film available from Asahi Glass Company.As seen in FIG. 3, the silicone 315 in the compression molding processillustrated fills the cavities 320 but further extends across the regionbetween and surrounding the cavities 320, to correspondingly result indeposition on the substrate 205 of a residual coating over a region ofthe front face of the substrate 205 including the contact 215. Such anadditional coverage of silicone 315 may occur due to the nature of thecompression molding process used to form the lens or optical element inembodiments of the present invention as described herein.

Referring now to FIG. 4, the assembly 200 is shown inserted in the mold305 during compression molding of the substrate 205 to form opticalelements on a front face of the substrate over the respectivesemiconductor light emitting devices 208. In some embodiments, thematerial used in forming the compression molded optical element andresidual coating is a silicone plastic and the compression moldingoccurs at a temperature of about 100° C. to about 150° C. (or about 140°C. in some embodiments) for a time of about three to about ten minutes(or about five minutes in some embodiments) at a pressure of about 0.1to about 0.6 tons/in². An example of a suitable silicone material foruse in forming packaged semiconductor light emitting devices in someembodiments of the present invention is organopolysiloxane mixture.

As seen in FIG. 5, after compression molding, the mold 305 is removed atthe release layer 310. As such, the assembly 200 includes a compressionmolded optical element 520 over each of the light emitting devices 208in addition to a residual coating 525 over a region of the front face ofthe substrate including the contacts 215. In other words, thecompression molded silicone layer 515 includes both the residual coating525 and the optical element 520 at the time of removal from the mold 305as shown in FIG. 5.

FIG. 5 further illustrates use of a removal method or process used toremove the silicone located on the mask 230 while leaving a molded lensover each light emitting device 208. As particularly illustrated in FIG.5, the removal process includes cutting the residual coating 525 in apattern corresponding to the mask 230 with a hot knife 530 or othercutting means having a pattern corresponding to the pattern cut into theresidual coating 525. In some embodiments, the hot knife 530 itself hasa corresponding pattern, allowing the cutting operation to be executedwith a single motion in the direction illustrated by the arrows in FIG.5 without the need for motion in a second direction. In some otherembodiments of the present invention, the cutting apparatus 530 mayfurther make a second or third directional movement to provide forcutting the residual coating 525 as desired to expose an electricalcontact portion of the contacts 215 without damaging the contacts 215.

The resulting packaged semiconductor light emitting device structureafter the removal operations illustrated in FIG. 5 according to someembodiments of the present invention is illustrated in FIG. 6. As seenin FIG. 6, the substrate 205 includes a plurality of light emittingdevices 208 with compression molded lenses 620 formed over correspondingones of the light emitting devices 208. The residual coating 525 over aregion of the front face of the substrate 205 including a contact areaof the contacts 215 has been removed, without damaging the contacts 215,to allow formation of electrical connections to the contacts 215.

Operations for forming a semiconductor light emitting device accordingto further embodiments of the present invention will now be describedwith reference to the flow chart illustration of FIG. 9. As shown inembodiments illustrated in FIG. 9, operations begin at block 900 byproviding a substrate 105, 205 having contacts 115, 215 on a front face107, 207 thereof (block 900). A semiconductor light emitting device 108,208 is mounted on the front face 107, 207 of the substrate 105, 205(block 905). The light emitting device 108, 208 is electricallyconnected to one or more of the contacts 115, 215 (block 905). Thus, thecontacts 115, 215 may provide means for electrically connecting thelight emitting device 108, 208 with other circuitry by forming anelectrical connection on the front face of 107, 207 of the substrate105, 205. An additional connection, or the connection referenced atblock 905, may be formed by attaching a wire bond electricallyconnecting a respective light emitting device 108, 208 to a contactportion of the substrate 105, 205 (i.e. the contact portion may be oneof the front side contacts 115, 215) (block 910).

In various embodiments, the substrate 105, 205 may be a ceramicsubstrate, a metal core printed circuit board (MCPCB), a flexiblecircuit substrate and/or a lead frame or the like. Furthermore, one ormore light emitting devices 108, 208 and front side contacts 115, 215may be provided in various respective arrangements on the substrate 105,205 in different embodiments of the present invention. Removal ofresidual coating from the contacts as needed may be provided based upona pattern suited to correspond to the selected geometry or arrangementof light emitting devices and front side contacts in various embodimentsof the present invention.

As shown in FIG. 9, a mask 230 is provided covering the front sidecontacts 115, 215 (block 915). The mask may be, for example, a polyimidefilm. The substrate is compression molded to form an optical element110, 620 on the front face of the substrate 107, 207 over respectiveones of the semiconductor light emitting devices 108, 208 and a residualcoating over a region of the front face of the substrate including thecontacts as will now be described with reference to block 920-940.

As seen in the illustrated embodiments of FIG. 9, compression moldingincludes providing a release layer 310 on a surface of the mold 305including a plurality of lens shaped cavities 320 positioned proximatecorresponding ones of the plurality of semiconductor light emittingdevices 108, 208 (block 920). The substrate is placed in the mold 305with the cavities positioned proximate corresponding ones of thesemiconductor light emitting devices (block 925). Silicone layer 315 isprovided in the mold 305 and the cavities 320 as well as a regionbetween and around the cavities 320 (block 930). The lenses 620, 110 arecompression molded from the silicone in the cavities (block 935). Thesubstrate, with a lens formed therein, is removed from the mold (block940).

Operations related to removing the residual coating over the contactswithout damaging the contacts will now be described for some embodimentsof the present invention with reference to blocks 945 and 950 of FIG. 9.The residual coating is cut in a pattern corresponding to the maskapplied as described at block 915 above (block 945). In some embodimentswhere the substrate includes a plurality of light emitting devices andcontacts on the front face, cutting the residual coating includescutting the residual coating with a hot knife. The hot knife may have apattern corresponding to the pattern cut in the residual coating so thatthe cutting operation may be provided by the advancement of the cuttingknife towards the substrate without lateral movement of the cuttingmember across the substrate. As such, the risk of any damage to thecontact surface during the removal process may be reduced. The mask andthe cut, overlying residual coating thereon are removed to expose thefront side contacts (block 950).

In some embodiments of the present invention, the light emitting device108, 208 is electrically connected to a contact portion by a wire bondbefore compression molding of the optical element 110, 620. Furthermore,in some embodiments, the substrate is compression molded to form theoptical element 110, 620 over the semiconductor light emitting device108, 208 and directly contacting the wire bond. A compression moldingprocess as described herein may allow such direct contact and formationof the optical element on both the wire bond and the associated lightemitting device while reducing or even preventing damage to the couplingbetween the light emitting device and the contact portion by the wirebond. In contrast, various other methods of forming a lens of such anarrangement may require the use of additional protective applications soas to avoid damaging the connection between the wire bond and the lightemitting device and the corresponding contact portion of a substrate.

Furthermore, in some embodiments of the present invention as describedherein, the light emitting device may be mounted flush on the front faceof the substrate and a compression molded optical element may be formedaround the light emitting device in a dome extending over a full 180degrees over the light emitting device. As such, a greater flexibilityand/or efficiency in extraction and provision of light from the lightemitting device may be provided through selection of the lens formingmaterial and any additives or the like added thereto as contrasted withapproaches requiring the use of a cavity of a reflective materialsurrounding the light emitting device. Such reflective cavitiesgenerally absorb at least some amount of the emitted light, while a lensor other optical element extending from the front face to fully surroundthe light emitting device mounted flush on the front face of thesubstrate may provide improved light extraction in various applications.However, in some embodiments, the LED could reside in a cavity orrecess.

While embodiments of the present invention using a mask have beendescribed with reference to FIGS. 3-6 and 9, it will be understood thatsome embodiments of the present invention do not use such a mask andcutting process. In some embodiments of the present invention, thesubstrate is a flexible circuit substrate and the residual coating isremoved by a wet solvent chemical cleaning of the substrate to removethe residual coating over the contacts. It will be understood that,whether a mask or wet etching approach is used, the residual coating maybe removed over a region of the front face of the substrate includingthe plurality of contacts but need not completely expose the contacts.However, a sufficient area of the contacts should be exposed to allowmaking of an electrical connection thereto without residual coatinginterfering with the electrical connection. A masking approach providedafter formation of the residual coating, as contrasted to prior tocompression molding, may be used in connection with the wet solventchemical cleaning operation so as to limit removal of residual coatingfrom desired areas in a selected pattern.

Packaged semiconductor light emitting devices according to furtherembodiments of the present invention will now be described withreference to the embodiments of FIGS. 7 and 8. Each include a plurality,illustrated as first and second, of optical elements formed on asubstrate. It will be understood that one and/or both of the respectiveoptical elements may be formed using compression molding in differentembodiments of the present invention.

As seen in the embodiments of FIG. 7, a packaged semiconductor lightemitting device 700 includes a plurality of semiconductor light emittingdevices 708 mounted flush on a front face 707 of a substrate 705. Afirst optical element 740 is formed over each of the semiconductor lightemitting devices 708. A second optical element 720 is formed over thefirst optical element 740 and the light emitting device 708. As furthershown in the embodiments of FIG. 7, an additive 742 may be added to thesecond optical element 720 to affect the light transmission or emissioncharacteristics of the semiconductor light emitting device 708. It willbe understood that the additive 742 may instead be added to the firstoptical element 740 or a same and/or different additive may be providedin each of the optical elements 720, 740. In addition, opticalproperties may be further tailored by selection of differentcharacteristics for the respective optical elements 720, 740, forexample, selecting a different refractive index for the respectivematerials to provide a desired effect in passage of light emitting fromthe semiconductor light emitting device 708. Additives to affect opticalproperties may include a phosphor, a scatter agent, a luminescentmaterial and/or other material affecting optical characteristics of theemitted light.

It will be understood that both the first and second optical elementsmay be compression molded in the embodiments of FIG. 7. However, infurther embodiments, the first optical element 740 may be formed byother means and the second optical element 720 may be formed bycompression molding generally as described above with reference to FIGS.3-6 and FIG. 8.

Further embodiments of a packaged semiconductor light emitting device800 are illustrated in FIG. 8. As seen in the embodiments of FIG. 8, asemiconductor light emitting device 808 is mounted flush on a front faceof a substrate 805. A wire bond 809 is shown making a connection betweenthe substrate 805 and the semiconductor light emitting device 808. Whilenot seen in FIG. 8, it will be understood that a second connection maybe formed at the interface between the light emitting device 808 and thefront face of the substrate 805.

A first optical element 84Q is formed proximate a light emitting device808 on the front face of the substrate 805. A second optical element 820is formed over the light emitting device 808, the wire bond 809 and thefirst optical element 840. As described with reference to FIG. 7, one orboth of the respective optical elements 840, 820 may be formed bycompression molding generally as described previously herein.Furthermore, the first optical element 840, while appearing as twodiscrete elements in the cross sectional view of FIG. 8, may be atoroidal shaped single optical element extending around the lightemitting device 808 and wire bond 809.

Further embodiments of methods for forming a packaged semiconductorlight emitting device will now be described with reference to theflowchart illustration of FIG. 10. More particularly, the methodsdescribed with reference to FIG. 10 may be used in forming the devicesillustrated in FIG. 7 or FIG. 8. For purposes of the description of FIG.10, embodiments in which both the optical elements are compressionmolded in an automated molding apparatus will be described. However, itwill be understood that the invention is not limited to suchembodiments. Furthermore, it will be understood the operations asdescribed with reference to compression molding may be used in someembodiments with the substrate having contacts on a front face thereofand removal of a residual portion of the molding material to expose thefront face contacts as described previously herein.

For the embodiments illustrated in FIG. 10, operations begin withproviding a substrate having a semiconductor light emitting device on afront face thereof (block 1000). As discussed previously, the substratemay include a plurality of semiconductor light emitting devices on thefront face thereof, such as illustrated in FIGS. 1 and 2. Furthermore,the semiconductor light emitting devices may be mounted flush on thefront face of the substrate without a reflector cavity. The substratemay be, for example, a ceramic substrate, a MCPCB, a flexible circuitsubstrate and/or a lead frame. However, the light emitting devices maybe mounted in a reflector cavity or the like.

Operations related to forming first and second optical elements of thepackaged semiconductor light emitting device will now be described withreference to blocks 1005-1030. The substrate is loaded in an automatedmolding apparatus including a first mold cavity configured to form thefirst optical element and a second mold cavity configured to form thesecond optical element (block 1005). The first and second mold cavitiesmay each include a plurality of lens shaped cavities positionedproximate corresponding ones of the plurality of semiconductor lightemitting devices where the substrate includes a plurality ofsemiconductor light emitting devices thereon. The substrate is moved tothe first mold cavity (block 1010). The movement may be by automatedconveyor, robotic arm and/or the like within the automated moldingapparatus.

The first optical element is compression molded on the front face of thesubstrate in the first mold cavity (block 1015). It will be understoodthat, while shown as compression molding at block 1015, the firstoptical element or the second optical element may be formed using aprocess other than compression molding, such as dispensing and/orbonding. Furthermore, the first optical element may be formed at block1015 proximate the semiconductor light emitting device but not coveringthe semiconductor light emitting device as illustrated, for example, bythe optical element 840 in FIG. 8. The first optical element may also insome embodiments be formed at block 1015 molded to and extending fromthe front face of the substrate in a region surrounding thesemiconductor light emitting device and extending over the semiconductorlight emitting device as shown for the first optical element 740 in theembodiments of FIG. 7. In some embodiments, where the first opticalelement does not extend over the light emitting device, the firstoptical element may be shaped to define a cavity with the semiconductorlight emitting device positioned in the cavity.

The substrate with the first optical element thereon is moved to thesecond mold cavity without requiring removal of the substrate from theautomated molding apparatus (block 1020). For example, a conveyor orrobotic tool, such as described with reference to operations at block1010, may also be used for operations at block 1020.

The second optical element is compression molded in the second opticalcavity (block 1025). As described with reference to the first opticalelement illustrated in FIG. 8, the second optical element may be moldedto extend from the front of the substrate in a region surrounding thesemiconductor light emitting device and extend over the light emittingdevice as seen with the second optical element 720 in FIG. 7 and thesecond optical element 820 in FIG. 8. The substrate with the first andsecond optical elements thereon is removed from the automated moldingapparatus (block 1030).

As also seen in both FIG. 7 and FIG. 8, the second optical element maybe compression molded over both the semiconductor light emitting deviceand the first optical element. The first optical element and the secondoptical element may have different refractive indexes selected toprovide a desired optical characteristic for the packaged semiconductorlight emitting device. The first and second optical element may beconfigured to provide a selected viewing angle to the packagedsemiconductor light emitting device. In some embodiments, the materialused in forming the first and/or second optical element has an adhesioncharacteristic selected to facilitate adhesion of the first opticalelement to the substrate during compression molding and/or to limitstress applied to the light emitting device and/or a wire bond coupledthereto during thermal cycling of the packaged semiconductor lightemitting device. The first optical element material and/or the secondoptical element material may include a phosphor. The first materialand/or the second material may be silicone, epoxy, a hybridsilicone/epoxy material and/or the like.

As described above, some embodiments of the present invention providepackaged semiconductor light emitting devices and methods for formingthe same using compression molding to produce lens having tailoredoptical properties. For example, light emitting devices packaged withcomposite lenses produced using compression molding may be provided. Insome embodiments, multiple compression molds may be used to producecompression molded lenses where both the first and the second opticalelements are compression molded to produce lenses having desired opticalproperties, such as viewing angles. In other embodiments, a firstoptical element may be dispersed, bonded or the like and the secondoptical element may be compression molded. As such, the first and secondoptical elements may have different properties (shape, composition,refractive index, and so on) tailored to the needs of the application ofthe packaged device. Some embodiments may also include additionaloptical elements, layers and/or compression molds in addition to thefirst and second optical element. Furthermore, the shape and compositionof each optical element may be different from one another and may betailored to provide a desired lamp performance. Improved adherenceand/or lower stress on compliant parts may be provided in variousembodiments of the present invention

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A method of packaging semiconductor light emitting device,comprising: providing a substrate having the semiconductor lightemitting device on a front face thereof and a contact on a front facethereof, wherein the light emitting device is electrically connected tothe contact on the front face of the substrate; and compression moldingan optical element on the front face of the substrate over thesemiconductor light emitting device and a residual coating over a regionof the front face of the substrate including the contact.
 2. The methodof claim 1, further comprising removing the residual coating over thecontact without damaging the contact.
 3. The method of claim 2, whereinproviding a substrate comprises: mounting the semiconductor lightemitting device on the front face of the substrate; and attaching a wirebond electrically connecting the semiconductor light emitting device toa contact portion of the substrate.
 4. The method of claim 3, furthercomprising mounting a second semiconductor light emitting device on aback face of the substrate and electrically connecting the secondsemiconductor light emitting device to a contact on the back face of thesubstrate.
 5. The method of claim 3, wherein compression moldingcomprises compression molding the substrate to form the optical elementover the semiconductor light emitting device and the wire bond anddirectly contacting the wire bond.
 6. The method of claim 2, wherein thesubstrate comprises a ceramic substrate, a metal core printed circuitboard (MCPCB), a flexible circuit substrate and/or a lead frame.
 7. Themethod of claim 2, wherein compression molding is preceded by providinga mask covering the front side contact and wherein removing the residualcoating comprises removing the mask.
 8. The method of claim 7, whereinthe mask comprises a polyimide film.
 9. The method of claim 7, whereinremoving the mask comprises: cutting the residual coating in a patterncorresponding to the mask; and removing the mask and the overlyingresidual coating thereon to expose the front side contact.
 10. Themethod of claim 9, wherein the substrate includes a plurality ofsemiconductor light emitting devices and contacts on the front facethereof and wherein compression molding comprises compression moldingthe substrate to form a plurality of optical elements on the front faceof the substrate over corresponding ones of the semiconductor lightemitting devices and a residual coating over a region of the front faceof the substrate including the plurality of contacts and wherein cuttingthe residual coating comprises cutting the residual coating with a hotknife, the hot knife having a pattern corresponding to the pattern cutin the residual coating.
 11. The method of claim 10, wherein the opticalelements comprise lenses and wherein compression molding comprises:placing the substrate in a mold including a plurality of lens shapecavities positioned proximate corresponding ones of the plurality ofsemiconductor light emitting devices; providing silicone into the mold;compression molding the lenses from the silicone in the cavities; andremoving the substrate with the lenses formed therein from the mold. 12.The method of claim 11, wherein providing silicone is preceded byproviding a release layer on a surface of the mold including thecavities and wherein removing the substrate comprises removing thesubstrate at the release layer.
 13. The method of claim 2, wherein thesubstrate comprises a flexible circuit substrate and wherein removingthe residual coating comprises wet solvent chemical cleaning thesubstrate to remove the residual coating over the contact.
 14. Themethod of claim 13, wherein the substrate includes a plurality ofsemiconductor light emitting devices and contacts on the front facethereof and wherein compression molding the substrate comprisescompression molding the substrate to form a plurality of opticalelements on the front face of the substrate over corresponding ones ofthe semiconductor light emitting devices and a residual coating over aregion of the front face of the substrate including the plurality ofcontacts.
 15. The method of claim 14, wherein the optical elementscomprise lenses and wherein compression molding comprises: placing thesubstrate in a mold including a plurality of lens shaped cavitiespositioned proximate corresponding ones of the plurality ofsemiconductor light emitting devices; providing silicone into the mold;compression molding the lenses from the silicone in the cavities; andremoving the substrate with the lenses formed therein from the mold. 16.The method of claim 2, wherein the optical element comprises a first anda second optical element and wherein compression molding comprises:compression molding the first optical element proximate thesemiconductor light emitting device; and compression molding the secondoptical element over the semiconductor light emitting device and thefirst optical element.
 17. The method of claim 16, wherein compressionmolding the first optical element comprises compression molding thefirst optical element over the semiconductor light emitting device. 18.The method of claim 2, wherein the optical element comprises a secondoptical element and wherein compression molding is preceded by forming afirst optical element proximate the semiconductor light emitting deviceand wherein compression molding the substrate comprises compressionmolding the second optical element over the semiconductor light emittingdevice and the first optical element.
 19. The method of claim 2, whereinthe optical element comprises a first optical element and whereincompression molding is followed by forming a second optical element overthe semiconductor light emitting device and the first optical element.20. A packaged semiconductor light emitting device, comprising: asubstrate having a contact on a front face thereof; a semiconductorlight emitting device mounted on the front face of the substrate; and acompression molded optical element on the front face of the substrateover the semiconductor light emitting device.
 21. The device of claim20, wherein the semiconductor light emitting device is mounted flush onthe front face of the substrate without a reflector cavity and whereinthe optical element is molded to and extends from the front face of thesubstrate in a region surrounding the semiconductor light emittingdevice and extends over the semiconductor light emitting device.
 22. Thedevice of claim 21, wherein the optical element comprises a secondoptical element and wherein the device further comprises a first opticalelement positioned proximate the semiconductor light emitting device andthe second optical element extends over the first optical element. 23.The device of claim 22, wherein the first optical element comprises acompression molded optical element.
 24. The device of claim 21, whereinthe compression molded optical element comprises a silicone lens. 25.The device of claim 21, wherein the semiconductor light emitting devicecomprises a plurality of semiconductor light emitting devices and thecontact comprises a plurality of contacts on the front face and whereinthe compression molded optical element comprises a plurality ofcompression molded optical elements over corresponding ones of thesemiconductor light emitting devices.
 26. The device of claim 25,wherein the optical elements comprise silicone lenses.